const PI = Math.PI;
module.exports = (radius) => {
  return {
    area() {
      return PI * radius * radius;   //圆面积
    },
    diameter(){
      return 2 * radius;     //直径
    },
    circumference() {
      return PI * 2 * radius;    //圆周长
    }
  };
};

console.log(module);
